Question

An inventor claims to have created a chemical cell that involves nickel and iron plates immersed in a secret solution. The cell has a characteristic voltage of 1.3 V. The cell has a mass of 100 g and the inventor claims a capacity of 250 A^.h. But is the inventor's claim physically impossible?

Answer 1

1 Ampere Hour = 1 Coulomb/Sec * 60*60 sec = 3600 Coulomb.

So, 250 A.h. capacity corresponds to a charge of (3600 * 250) Coulomb = 900000 Coulomb

1 mole of electrons contains 96500 Coulomb.

So, number of moles of reactant required to give a capacity of 250 A.h. Capacity is

                (900000/96500) moles = 9.33 moles

Molar mass of the reactants are Ni (58.69 g) and Fe (55.84 g).

Thus in 100 g of Chemical Cell it is not possible to accomodate 9.33 moles of reactant.

Hence, the inventor's claim is physically impossible.